Computer networks have become ubiquitous. One type of network technology is known as Shortest Path Bridging (SPB). SPB in computer networking is a technology that greatly simplifies the creation and configuration of carrier, enterprise, and cloud networks which virtually eliminates human error, while enabling multipath routing. SPB allows all paths to be active with multiple equal cost paths, provides much larger layer 2 topologies, faster convergence times, and improves the use of the mesh topologies through increase bandwidth and redundancy between all devices by allowing traffic to load share across all paths of a mesh network.
In an SPB network packets are encapsulated at the edge in Media Access Control (MAC)-in-MAC and transported only to other members of the logical network. Unicast and multicast are supported and all routing is on symmetric shortest paths. Many equal cost shortest paths are supported. As SPB networks become more widely deployed, it is anticipated that network operators would try to connect multiple independently operated SPB networks to one another in a peering model.
One reason for connecting multiple independently operated SPB networks to one another is to provide transport services that interconnect multiple segments of a private SPB network. Another reason is to break up a large SPB network into multiple smaller SPB networks for reasons of scale, ease of administration, and the like.
In such scenarios a mechanism is needed that allows the number of node, services and the resulting multicast forwarding state in each SPB network to grow independent of the limitations of the other SPB networks that it might be connected to. Left unaddressed this can cause an unmanageable explosion in the multicast forwarding table size.